Depends on the company. At my current workplace, the candidate is given an option to provide feedback at the end (either through a form or an email), and all interviewers are also required to submit written notes on how everything went down.

Given that a candidate at the onsite will get interviewed by 4-5 people, with each of them providing a very detailed set of notes, it would be fairly trivial to smell out a misbehaving interviewer, if one cared to do so. What actually happens at the end of the day with those notes and candidate feedback, that’s the part i am not sure about. Once they get submitted to the hiring committee (or HR), it is out of my hands.

But just saying, they do have ways of evaluating it, just on a less precise scale and more on a “bad/good enough/amazing” scale. With only the “bad” outcome raising any eyebrows/having any meaningful effect, and with 99% of them getting the “good enough”/“amazing” ratings. And how often the signal for that “bad” rating gets caught is also not something I know much about.

P.S. Your assessments and notes are all preserved in the centralized hub, so you (and some others) can always access them later as well. And, sometimes, you indeed have people checking them out for assessment or such. Especially during your first couple interviews, you have a person supervising you and taking notes in parallel as well, and then you discuss them and they give you improvement suggestions and such.